Neural stimuli elicit long-term changes in target neurons, potentially by altering gene expression. However, the mammalian nervous system's extensive complexity has hindered establishing messenger RNA (mRNA) transcription as a major cellular control point for neuronal influences. The objective of this research is to determine how neurotransmitters modulate specific gene expression, using the gene for the catecholamine- synthesizing enzyme phenylethanolamine N-methyltransferase (PNMT) in primary bovine adrenal chromaffin cells as a powerful model system. This study will: 1) Investigate the ability of the neurotransmitter acetylcholine to modulate specific gene transcription. Nicotinic and muscarinic effectors of PNMT mRNA production will be evaluated using quantitative hybridization and nuclear run-on assays. Additionally, it will be possible, for the first time, to modulate transient expression of a neural gene in terminally-differentiated primary cells by transfecting chromaffin cultures with a PNMT promoter-reporter gene construct. 2) Resolve the role of intracellular second messengers as mediators of cholinergic regulation. Changes in PNMT gene transcription will be correlated with calcium mobilization, inositol phospholipid hydrolysis and cyclic nucleotide production. The fact that the PNMT message can be modulated through several second messenger systems underscores its value as a model system for analyzing the interactions of neural stimuli at the level of gene expression. 3) Correlate functional regulation of transcription with structural analysis of the gene. Identification of intracellular second messenger intermediates will form the basis for a search of neurally responsive elements encoded in the PNMT gene. By linking PNMT epinephrine (adrenaline) production with long-term gene- related adaptations to chronic stress, these studies will furnish an essential framework for future analyses of PNMT synthesis in the central nervous system. Additionally, since epinephrine neurons may regulate the autonomic nervous system, particularly with regard to circulation, it is critical that their role be fully explored with regard to cardiovascular, metabolic, and endocrine responses, as well as in the pathogenesis of certain circulatory diseases (e.g., essential hypertension) and mental disorders (e.g. manic depressive illness). It therefore becomes paramount that epinephrine production be understood at its most fundamental level, transcription of the PNMT gene.